191. Number of 1 Bits

Write a function that takes an unsigned integer and returns the number of ’1′ bits it has (also known as the Hamming weight).

For example, the 32-bit integer ’11′ has binary representation 00000000000000000000000000001011, so the function should return 3.

//数出十进制转换成二进制后的数有多少个1，亦或本身减一然后计数

public class Solution {
    // you need to treat n as an unsigned value
    public int hammingWeight(int n) {
        int count = 0;
        while(n!=0){
            count++;
            n = n & (n-1);
        }
        return count;
    }
}